Gas compressors are used for many items in the consumer market (to inflate basketballs, toys and tires) and in the industrial market (to liquify gas, compress gas for transport fuel, for powering pneumatic tools and for distributing natural gas from the well head to the user).
The efficiency of prior art commercial gas compressors is poor primarily because practicalities require that the gas be compressed rapidly. Rapid compression makes it nearly impossible to dissipate the heat of compression during the compression process. This inherent heating during the compression process (herein “C-heat”) demands up to 100% more physical work from the prime mover than if the same process was done with complete and immediate “C-heat” removal. Typically, the prime mover is an internal combustion engine or an electric motor. A rapid compression process with little or no C-heat heat removal is called an adiabatic compression. Most state of the art compressors operate with adiabatic or semi-adiabatic compression cycles. The energy or work lost due to C-heat increases as the final target pressure for the compressor increases. This why multiple stages of compression, with intercoolers in-between, are used to reach high final pressures.
The work potential of the compressed gas is roughly equivalent to the work required to compress the gas, if the compressed gas is used rapidly while it is still hot. However, most compressed gas is stored in an uninsulated pressure vessel and the time between the compression of the gas and the use of the gas makes retention of the heat in the gas impractical. Therefore, this 50-100% additional work to overcome the C-heat while compressing the gas is lost or wasted. Compression performed while immediately removing all of the C-heat is called isothermal compression. If isothermal compression can be achieved, the energy required to compress gas to a given pressure could theoretically be cut nearly in half. Stated otherwise, twice the amount of compressed, gas could be produced for the same cost in energy or dollars. Historically isothermal compression has been impractical or impossible to achieve because the C-heat removal from the compressed gas requires too much time and/or internal heat transfer surface area for practical use.
One type of prior art compressor that demonstrates rapid isothermal compression is U.S. Pat. No. 892,772 to Taylor, patented in 1908. Taylor '772 discloses a hydraulic air compressor which utilizes a falling column of water infused with millions of tiny spherical bubbles. When the column of water falls from a particular height, the bubbles in the water are compressed. The Taylor '772 system used a 70 foot differential head pressure (about 21 meters) which creates approximately 128 psi (pounds per square inch) pressure to drive 5000-6000 horsepower isothermal compressors.
In order to make hydraulic bubble, isothermal compressors portable and practical, U.S. Patent Application Publication No. 20150023807 to Cherry et at, (“Cherry '807”) Ser. No. 14/280,780, filed May 19, 2014 (the contents of which is incorporated herein by reference thereto) discloses the use of centrifugal force to shrink the physical size of a column of water necessary to reach industrial pressures by at least 1000 times. Centrifugal force acts on gas bubbles entrained between liquid slugs moving radially outward (distally away from the axis of rotation) through the capillary compression tubes which may be radial, tangential or continuously curved. Compressed gas is collected in the annular pressurized gas separation and storage chamber, whereupon it is harvested for industrial use. A gas-liquid emulsion is fed to the capillary compression tubes by an inboard emulsification device. The emulsification device may include a vortex generator, an ejector or a venturi injector, all feeding the gas-liquid mixture into the inboard ends of the capillaries. The capillaries are formed in a series of discs, coaxially stacked with outer disc ends open to the annular space.
U.S. Patent Application Ser. No 62/222,261, filed Sep. 23, 2015 to Cherry et al (“Cherry '261”) (the contents of which is incorporated herein by reference thereto) discloses improvements to the device and methods disclosed in Cherry et al '807 using directional flow restriction technology to ensure that emulsion flow through the capillary compression tubes of a centrifugal bubble compressor move only in a radially outward direction.
U.S. Pat. No. 6,276,140 to Keller discloses a device to generate energy through a turbine engine. The Keller '140 device also uses, falling water fed through a funnel shaped vertical tube or tunnel in order to compress air bubbles in the falling water. The waterfall drop in Keller '140 was between 30-100 meters. Typical diameters at the top of the Keller '140 funnel tube are approximately 2-7 meters and, at the bottom, the funnel outlet region is typically 0.7-2.0 meters.
U.S. Pat. No. 1,144,865 to Rees discloses a rotary pump, condenser and compressor. However, the Rees '865 rotary pump compressor utilized large cavities having highly curved shaped walls and the cavities were not radial with respect to the rotating container.
U.S. Patent Application Publication No. 2011/0030359 to Fong entitled Compressed Air Energy Storage System Utilizing Two-Phase Flow to Facilitate Heat Exchange (Ser. No. 12/686,695, filed Aug. 25, 2010) generally discusses a centrifugal separator in paragraphs 0963, 0964, 0959 and 0983. However, Fong '359 does not provide of a centrifugal separator.
U.S. Patent Application Publication No. 2011/0115223 to Stahlkopf entitled Compressed Air Energy Storage System Utilizing Two-Phase Flow to Facilitate Heat Exchange (Ser. No. 13/010,683, filed Jan. 20, 2011) also discusses centrifugal separators.
Neither Fong '359 or Stahlkopf '223 discuss a centrifugal compressor which compresses bubbles in water or a liquid in an isothermal manner to extract the compressed air or gas.
U.S. Pat. No. 1,769,260 to Hughes discloses a centrifugal pump and condenser that uses capillary tubes to compress gas bubbles in a similar manner to this device, however it differs in several important ways. The manner in which Hughes '260 creates a bubble train (see gas receiving chamber 21) results in much longer and larger bubbles, which larger bubbles have correspondingly greater buoyancy and this greater buoyancy make it very difficult to force these larger bubbles towards the distal end of the compression tube than the fine emulsion in the Cherry '807 and '261 disclosures. The shroud 24 in Hughes '260 is a trough that collects water as the water leaves the capillary chambers 22 at their radially distal ends. The trough fills with water trapped due to centrifugal force at a depth determined by the inward facing flanges 25, “over” which excess water drains to the inside wall of stationary cylindrical casing 10. The radially outboard ends of the capillary chambers 22 extend radially beyond the internal diameter of the inward facing flanges 25, creating a gas seal.
In Hughes '260, the shroud 24 is similar to the rotating housing in Cherry '807, Ser. No. 14/280,780, filed May 19, 2014, in the sense that the ends of the compression tubes are radially (and hydraulically) below the level of the drain on the cover plate, creating a gas seal. The Cherry '807 design is different by virtue of the fact that the rotating housing is not just a gas seal but also acts as a pressurized gas storage housing and a gas/liquid separation chamber as well, whereas Hughes' shroud has no significant pressure differential. The Hughes shroud 24 does act as a seal but does not act as a rectifying agent to enforce unidirectional distal flow as this device does.
The present invention expands upon the method and system in Cherry '807 which relies on centrifugal force to enhance the weight of intermediate liquid slugs acting on entrained gas bubbles moving through the micro-channel capillary tubes which enhanced weight in a rotary environment overcomes bubble buoyancy and causes the bubbles to transit through the capillary tubes to an outer radial position (stated otherwise, the bubbles “sink” to the outside of rotation), absorbing the heat of compression and thereby isothermally compressing the gas.
The present invention also builds upon the Cherry '261 method and system by creating, enforcing and enhancing distally oriented unidirectional emulsion flow in the capillary compression tubes with the use of mechanical checking or prohibition of reverse flow, the dynamic enforcement of distal (that is generally radially outward) emulsion flow, checking or prohibiting bubble buoyancy which is contrary to the radially outboard movement of the bubbles towards the distal ends of the tubes, which buoyancy is counter the emulsion exit velocity, and tapering the tube diameters longitudinally to match the rate of bubble diameter reduction during compression.
The general focus of Cherry '807 and '261 is the isothermal compression of gas in a rotating bubble compressor. In earlier constructs of the Cherry '807 and '261 devices, some energy imparted to the water in the impeller/compression tube device is recovered in the design of the drain race. This energy recovery occurs, by converting the high angular momentum of the water entering the drain race into shaft torque. This torque conversion occurs by forcing the water to slow down due to the presence of radial vanes in the drain race. The principle of torque conversion is the same principle that many hydroelectric turbines rely on to convert angular momentum in water to shaft torque in order to generate electricity at a hydroelectric facility.
As explained in a prior art reference entitled “Turbines”, by J. B. Calvert, February 2010, torque is the rate of change of angular momentum, just as force is the rate of change of linear momentum. When a fluid exerts a torque on a turbine runner, the reaction is a change in angular momentum of the fluid. Fluid is given angular momentum by the guide vanes which, ideally, is converted to by the torque exerted on the runner. With some machines, however, the water at the exit, may still have considerable angular momentum, and the energy in this motion is energy that does not appear at the shaft.